/*
 * Copyright 2002-2009 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.util;

import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Package-protected helper class for {@link AntPathMatcher}. Tests whether or not a string matches against a pattern
 * using a regular expression.
 *
 * <p>The pattern may contain special characters: '*' means zero or more characters; '?' means one and only one
 * character; '{' and '}' indicate a URI template pattern.
 *
 * @author Arjen Poutsma
 * @since 3.0
 */
class AntPathStringMatcher {

   private static final Pattern GLOB_PATTERN = Pattern.compile("\\?|\\*|\\{([^/]+?)\\}");

   private static final String DEFAULT_VARIABLE_PATTERN = "(.*)";

   private final Pattern pattern;

   private String str;

   private final List<String> variableNames = new LinkedList<String>();

   private final Map<String, String> uriTemplateVariables;

   /** Construct a new instance of the <code>AntPatchStringMatcher</code>. */
   AntPathStringMatcher(String pattern, String str, Map<String, String> uriTemplateVariables) {
      this.str = str;
      this.uriTemplateVariables = uriTemplateVariables;
      this.pattern = createPattern(pattern);
   }

   private Pattern createPattern(String pattern) {
      StringBuilder patternBuilder = new StringBuilder();
      Matcher m = GLOB_PATTERN.matcher(pattern);
      int end = 0;
      while (m.find()) {
         patternBuilder.append(quote(pattern, end, m.start()));
         String match = m.group();
         if ("?".equals(match)) {
            patternBuilder.append('.');
         }
         else if ("*".equals(match)) {
            patternBuilder.append(".*");
         }
         else if (match.startsWith("{") && match.endsWith("}")) {
            int colonIdx = match.indexOf(':');
            if (colonIdx == -1) {
               patternBuilder.append(DEFAULT_VARIABLE_PATTERN);
               variableNames.add(m.group(1));
            }
            else {
               String variablePattern = match.substring(colonIdx + 1, match.length() - 1);
               patternBuilder.append('(');
               patternBuilder.append(variablePattern);
               patternBuilder.append(')');
               String variableName = match.substring(1, colonIdx);
               variableNames.add(variableName);
            }
         }
         end = m.end();
      }
      patternBuilder.append(quote(pattern, end, pattern.length()));
      return Pattern.compile(patternBuilder.toString());
   }

   private String quote(String s, int start, int end) {
      if (start == end) {
         return "";
      }
      return Pattern.quote(s.substring(start, end));
   }

   /**
    * Main entry point.
    *
    * @return <code>true</code> if the string matches against the pattern, or <code>false</code> otherwise.
    */
   public boolean matchStrings() {
      Matcher matcher = pattern.matcher(str);
      if (matcher.matches()) {
         if (uriTemplateVariables != null) {
            for (int i = 1; i <= matcher.groupCount(); i++) {
               String name = this.variableNames.get(i - 1);
               String value = matcher.group(i);
               uriTemplateVariables.put(name, value);
            }
         }
         return true;
      }
      else {
         return false;
      }
   }

}
